We can see usage of the "pipe" operator |> in the above code.
The operator might look familiar if you have some *nix background.
In F#, the |> operator basically means: take the value on the left side and apply it to the function on the right side of the operator.
In this very case it simply means: invoke the htmlToString function on the HTML object model.

Let's test the index view in our App.fs:

App.fs

18:

path"/">=> (OKView.index)

If you navigate to the root url of the application, you should see that proper HTML is now being returned.